Evaluation of Bedding Plant Varieties for Resistance to Phytophthora

Abstract

Abstract Seedlings of several annual and perennial bedding plant species were inoculated with an isolate of Phytophthora nicotianae (synonym = P. parasitica) and planted into field beds in a simulated landscape situation. Throughout the growing season, growth measurements and disease ratings of the inoculated plants were compared with those of non-inoculated control plants of the same species in identical beds. Phytophthora-inoculated plants that continued to thrive through most of the growing season included Ageratum houstonianum, Celosia ‘Apricot Brandy’, and ‘New Look’; Dahlia ‘Harlequin’; Eustoma grandiflorum (prairie gentian); Lobularia ‘Carpet of Snow’; Nicotiana ‘Alta Dwarf White’, ‘Domino Salmon’, and ‘Nicki Red’; Pelargonium (geranium) ‘Multibloom Scarlet Eye’; Petunia ‘Polo Salmon’, and ‘Sugar Daddy’; Portulaca ‘Sundial Peppermint’; Rudbeckia ‘Rustic Dwarf’; Salvia ‘Lady in Red’, and ‘Victoria Blue’; Tagetes (marigold) ‘Disco Mix’, ‘Inca Orange’, ‘Inca Yellow’, ‘Janie Harmony Improved’, and ‘Gold Fireworks’; and Zinnia angustifolia. Plants that performed poorly following inoculation with Phytophthora include Antirrhinum (snapdragon) ‘Liberty White’, and ‘Liberty Mix’; Catharanthus (vinca) ‘Little Bright Eye’, and ‘Tropicana Rose’; Hibiscus ‘Disco Belle Mix’; Impatiens ‘Accent Bright Eye’; Leucanthemum x ‘Alaska’; Melampodium ‘Medallion’; Salvia ‘Turkestanica’; Torenia ‘Clown Mix’; Verbena ‘Imagination’; and Viola (pansy) ‘Fama See Me’. This study identifies bedding plant taxa which will provide an acceptable display in landscape beds infested with Phytopthora nicotianae (synonym = P. parasitica).